Study on the Thermal Cracking and Gas Generation at the Insulation Interface of High-Voltage Cable Intermediate Joints

The intermediate joint of high-voltage cables, as a key component for connecting cables, plays a crucial role in the reliability of the system, which directly impacts the stability and safety of the power grid. However, due to the special installation location and complex installation process of the high-voltage cable intermediate joints, they are more prone to overheating, discharge phenomena, and even explosion accidents. Cable intermediate j oint failures primarily originate from interface discharge at the interface between silicone rubber (SiR) and cross-linked polyethylene (XLPE) insulation. Therefore, this paper investigates the gas generation phenomenon at the insulation interface of high-voltage cable intermediate joints during the discharge-induced thermal cracking process. First, the gas generation mechanism under the temperature rise due to discharge at the SiR-XLPE interface of the cable intermediate j oint is analyzed. Then, discharge-induced thermal cracking tests at the SiR-XLPE insulation interface are conducted, with the generated gases being collected and analyzed for their composition. Finally, a simplified model of heat generation and temperature rise in the discharge channel at the insulation interface is established. The results show that the temperature in the discharge channel at the insulation interface is much higher than the thermal cracking temperature of the material, leading to the thermal cracking of the insulation material and the generation of gas.